Image forming apparatus with heat exhausting means for exhausting air from around a fixing unit and a delivery tray

ABSTRACT

A copying machine  100  is provided with an image forming portion  115  for forming a toner image on a sheet, a fixing device  122  for applying heat to the sheet to fix the toner image on the sheet, a delivery portion  125  on which the sheet is delivered and stacked, heat exhausting fans  157  and  158  provided in the vicinity of the fixing device  122  and the delivery portion  125  for exhausting air in the surroundings of those  122, 125  from the right side  101   b  of the main body  101 . There is provided air vents  162, 163  and  164  between the fixing device  122  and the heat exhausting fans  157, 158  and between the delivery portion  125  and the heat exhausting fans  157  and  158 . Thus, heat of the fixing device  122  is exhausted to avoid the delivered sheet adhesion caused by the high temperature.

TECHNICAL FIELD

The present invention relates to an image forming apparatus, such as acopying machine or a laser beam printer etc., for forming a toner imageon a sheet.

BACKGROUND ART

There are conventional image forming apparatus, such as copying machinesor laser beam printers (LBP), which form images on sheets.

In FIG. 8, a copying machine as an example of such an image formingapparatus is shown. The copying machine 10 is provided with a documentstand 2 composed of a transparent glass plate that is fixed to the topportion of the main body 1 of the copying machine 10. A documentpressure cover 3 is configured to press a document D that is beingplaced at a predetermined position on the document stand 2 with itsimage surface facing downward, against the document stand 2 toimmobilize it. Beneath the document stand 2, there is provided anoptical system composed of a lamp 4 for illuminating the document D,reflection mirrors 5, 6 and 7 for directing a reflected light image ofthe document D to an image processing unit 8 and an imaging lens 11. Thelamp 4 and the reflection mirrors 5, 6 and 7 are adapted to be moved inthe direction indicated by arrow a at a predetermined speed so as toscan the document D.

An image forming portion 15 includes a photosensitive drum 12, a charger13 for charging the surface of the photosensitive drum 12 uniformly, adeveloping device 14 for forming a toner image on the photosensitivedrum 12, a transferring charger 19 for transferring the toner imageformed on the photosensitive drum 12 onto a sheet S, a stripping charger20 for stripping the sheet S, on which the toner image has beentransferred, from the photosensitive drum 12, and a cleaner 26 forremoving toner remaining on the photosensitive drum 12 after the tonerimage has been transferred. The photosensitive drum 12 is adapted insuch a way that an electrostatic latent image is formed, by a lightimage radiated by a laser unit 9, on the surface of the photosensitivedrum 12 that has been charged by the charger 13 and then theelectrostatic latent image is developed and transferred onto the sheetS. The sheet S is fed from a sheet cassette 27.

In the downstream of the image forming portion 15, there is provided insequence, a transport portion 21 for transporting the sheet S on whichthe toner image has been transferred, a fixing device 22 for fixing thetoner image on the sheet S transported by the transport portion 21 tothe sheet as a permanent image, and a delivery roller pair 24 fordelivering the sheet S on which the toner image has been fixed by thefixing device 22, from the main body 1 of the copying machine. Thecopying machine has a delivery portion 25 provided externally of itsmain body 1 for receiving the sheet S delivered by the delivery rollers24.

There is another type of copying machine such as a copying machine 16shown in FIG. 9 that has an in-body delivery structure in which sheetsare delivered inside its main body in order to save space. The imageforming process of this copying machine 16 is substantially the same asthat of the copying machine 10 shown in FIG. 8, though a sheet transportpath 53 of the transfer portion is configured to guide sheets S in thevertical direction. In addition, a transfer roller 50 is used in placeof the transfer charger 19 shown in FIG. 8. In the copying machine 16shown in FIG. 9, the sheet transport path 53 is provided in the rightside portion of the main body 1 of the apparatus. Therefore, a fan 54 isprovided on the side of the left side wall of the main body 1 of theapparatus so as to cause air in the main body of the machine to flowfrom the right to the left of the main body 1 of the apparatus.

There is also another type of copying machine 28 shown in FIG. 10, whichis additionally provided with a rotary developing unit 51 and anintermediate transfer belt 52 etc. for forming a color image. Thiscopying machine 28 uses a charging roller 60 in place of the charger 13shown in FIG. 8.

The fixing device 22 of each of the copying machines 10, 16 and 28 isadapted to nip and transport the sheet while applying heat and pressureto it so as to fix the toner image on the sheet.

In connection with the above descriptions, components of the copyingmachines 16 and 28 that operate in the same manner as the correspondingcomponents of the copying machine 10 are designated with the samereference signs as the components of the copying machine 10, and thedescriptions of those components are omitted.

In the structure like that shown in FIG. 10, in which a fan 55 isprovided on the side of the left side wall of the main body 1 of theapparatus to cause air to flow from the right to the left of the mainbody 1 of the apparatus, there is a risk that the heat generated by thefixing device 22 might be transferred to the rotary developing unit 51and the intermediate transfer belt 52 etc. The rotary developing unit 51and the intermediate transfer belt 52 are processing units that usetoner, and therefore if their temperatures increase excessively,troubles such as toner blocking or fusion bonding of toner can occur.

In the copying machines 16 and 28 shown in FIGS. 9 and 10, in whichsheets are transported vertically along the sheet transport path 53, thedistance between the fixing device 22 that fixes toner images on sheetsand the delivery portion 25 that delivers the sheets is relatively smallas compared to the copying machine 10 shown in FIG. 8, in which sheetsare transported horizontally. Therefore, the temperature of the sheetsdelivered to the delivery portion 25 is high, and so sheets can stick oradhere to each other due to toner images that have not been cooledsufficiently (such phenomena will be referred to as “delivered sheetadhesion” hereinafter).

In addition, the fan 56 of the copying machine 10 shown in FIG. 8 isdisposed in the rear side portion of the main body 1 of the apparatusand in the vicinity 61 of the fixing device 22. The fan 54 of thecopying machine 16 shown in FIG. 9 is disposed in the vicinity 62 of theleft side wall of the main body 1 of the apparatus. The fan 57 of thecopying machine 28 shown in FIG. 10 is disposed in the rear side portionof the main body 1 of the apparatus and in the vicinity 63 of the fixingdevice 22. Therefore, when the fans 56, 54 and 55 are to be replaced dueto any trouble, a service person is required to approach to the leftside wall or the rear side of the main body 1 of the apparatus forreplacement operations. In addition, the above-described arrangements ofthe fans not only require a long time for maintenance operations butalso require the copying machine to be shut down for a long time (i.e.downtime is long).

Furthermore, in the copying machine 16 shown in FIG. 9, in which sheetsS are transported vertically along the sheet transport path 53, theleading edges of the sheets may bend to the right or left, and thereforethey are often transported under unstable states. Especially, after asheet has left the fixing device 22 and until it reaches the deliveryportion 25, the sheet is apt to be curled due to heat and pressureapplied by the fixing device 22, and so it is required to enable stabletransportation of the sheets.

Since the fan 57 of the copying machine 28 shown in FIG. 10 is disposedin the rear side portion of the main body 1 of the apparatus and thefixing device 22 is arranged longitudinally in the direction transverseto the direction of the sheet transportation (i.e. the longitudinaldirection coincides with the direction perpendicular to the plane of thedrawing sheet of FIG. 10), the heat of the fixing device 22 is exhaustedat one end of the fixing device 22, and therefore the efficiency of heatexhaust is low.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an image formingapparatus that can exhaust the heat generated by fixing means thatgenerates heat to prevent the delivered sheet adhesion due to hightemperature from occurring.

An image forming apparatus with heat exhausting means that attains theabove object comprises:

image forming means for forming a toner image on a sheet;

fixing means for applying heat to the sheet on which the toner image hasbeen formed by the image forming means so as to fix the toner image onthe sheet;

delivering and stacking means on which the sheet, on which the tonerimage has been fixed by the fixing means, is to be delivered andstacked; and

heat exhausting means provided in the vicinity of the fixing means andthe delivering and stacking means, for exhausting air in thesurroundings of the fixing means and air in the surroundings of thedelivering and stacking means from a side portion of a main body of theapparatus,

wherein air vents are provided between the fixing means and the heatexhausting means and between the delivering and stacking means and theheat exhausting means, respectively.

In the image forming apparatus with heat exhausting means according tothe invention, the delivering and stacking means may be disposed abovethe fixing means, and the image forming apparatus may further comprise asheet transport path arranged in a vertical direction between the fixingmeans and the delivering and stacking means, the sheet transport pathhaving an air vent.

The image forming apparatus with heat exhausting means according to thepresent invention may further comprise heat exhaust control means forcontrolling, while the sheet is transported in the sheet transport path,the heat exhausting means in such a way as to reduce an air exhaustamount of the heat exhausting means as the sheet approaches from thefixing means to the delivering and stacking means.

In the image forming apparatus with heat exhausting means according tothe present invention, the heat exhausting means may be disposed on alid that is provided on a side portion of the main body of theapparatus.

In the image forming apparatus with heat exhausting means according tothe present invention, the lid may be provided in such a way that thelid is openable and closable with a pivot being located at the rear sideof the side portion of the main body of the apparatus.

These and other objects, features and advantages of the presentinvention will become more apparent upon consideration of the followingdescription of the preferred embodiments of the invention taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an intermediate portion with respect tothe height direction of a copying machine as an image forming apparatusaccording to the first embodiment of the present invention.

FIG. 2 is a cross sectional front view showing the copying machine asthe image forming apparatus according to the first embodiment of thepresent invention.

FIG. 3 is a cross sectional view showing a portion including heatexhausting fans of the copying machine as the image forming apparatusaccording to the first embodiment of the present invention.

FIG. 4 is a plan view showing an intermediate portion in the heightdirection of a copying machine as an image forming apparatus accordingto the second embodiment of the present invention.

FIG. 5 is a cross sectional front view showing the copying machine asthe image forming apparatus according to the second embodiment of thepresent invention.

FIG. 6 is a cross sectional view showing a portion including heatexhausting fans of a copying machine as an image forming apparatusaccording to the third embodiment of the present invention.

FIG. 7 is a cross sectional view of the portion shown in FIG. 6, showinga state in which a sheet is wrinkled.

FIG. 8 is a cross sectional front view showing a copying machine as aconventional image forming apparatus.

FIG. 9 is a cross sectional front view showing a copying machine as aconventional image forming apparatus.

FIG. 10 is a cross sectional front view showing a copying machine as aconventional image forming apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following, the present invention will be described with referenceto the drawings in connection with image forming apparatus in the formof copying machines as embodiments of the present invention. The imageforming apparatus according to the present invention has a unit, e.g. afixing device that generates heat in the interior of the main body ofthe apparatus. Such image forming apparatus includes a printer and otherapparatus, besides a copying machine. Therefore, the image formingapparatus according to the present invention is not limited to a copyingmachine.

(Copying Machine According to First Embodiment)

In the following, a copying machine according to a first embodiment ofthe invention will be described with reference to FIGS. 1, 2 and 3. FIG.1 is a plan view of the copying machine. FIG. 2 is a cross sectionalfront view of the copying machine. FIG. 3 is a detailed view showing aportion around a fixing device 122 and a delivery portion 125.

As shown in FIG. 2, the copying machine 100 is provided with a documentstand 102 composed of a transparent glass plate that is fixed to the topportion of the main body 101 of the machine. A document pressure cover103 is configured to press a document D that is being placed in apredetermined position on the document stand 102 with its image surfacefacing downward, against the document stand 102 to immobilize it.Beneath the document stand 102, there is provided an optical systemcomposed of a lamp 104 for illuminating the document D, reflectionmirrors 105, 106 and 107 for directing a reflected light image of thedocument D to an image processing unit, and an imaging lens 111. Thelamp 104 and the reflection mirrors 105, 106 and 107 are adapted to bemoved in the direction indicated by arrow b at a predetermined speed soas to scan the document D.

An image forming portion 115 includes a photosensitive drum 112, acharging roller 160 for charging the surface of the photosensitive drum112 uniformly, a rotary developing unit 151 for forming a toner image onthe photosensitive drum 112, an intermediate transfer belt 152 ontowhich the toner image having been developed on the photosensitive drum112 is transferred, a transfer roller 150 for transferring the tonerimage on the intermediate transfer belt 152 onto a sheet S, and acleaner 126 for removing toner remaining on the photosensitive drum 112after the transfer of the toner image. The photosensitive drum 112 isadapted in such a way that an electrostatic latent image is formed, by alight image radiated by a laser unit 109, on the surface of thephotosensitive drum 112 that has been charged by the charging roller 160and then the electrostatic latent image is developed and transferredonto the intermediate transfer belt 152. The toner image on theintermediate transfer belt 152 is transferred by the transfer roller 150onto the sheet S. The sheet S is passed out from a sheet cassette 127 bya pickup roller 128 and fed by a retard roller pair 129 that separatesand feeds only one sheet, and the sheet S is further transported bytransport roller pairs 130, 131, 132, 133, 134 to the position in whichthe transfer is performed.

Above the image forming portion 115 and in the downstream of it in thetransport direction, there is provided in sequence, a fixing device 122for fixing the toner image on the sheet S that is being transported as apermanent image and a delivery roller pair 124, disposed above thefixing device 122, for delivering the sheet S on which the toner imagehas been fixed by the fixing device 122, from the main body 101 of thecopying machine. The copying machine 100 has a delivery portion 125provided externally of its main body 101 to receive the sheet Sdelivered by the delivery roller pair 124.

As shown in FIG. 3, heat exhausting fans 157 and 158 are provided on ajammed sheet clearance door 159 in the right side portion 101 b of thehousing of the main body 101 of the copying machine 100. The jammedsheet clearance door 159 has a plurality of exhaust openings 166 formedat the portion on which the heat exhausting fans 157 and 158 aremounted. In the left side portion (or wall) of the housing of the mainbody 101 opposed to the heat exhausting fans 157 and 158 and in a wall153 a of a sheet transport path 153, and in the vicinity of the fixingdevice 122, there is provided a plurality of air vents 162 a, 162 b, 163a, 163 b, 164 and 168 through which air passes. In addition, as shown inFIG. 2, a plurality of intake openings 165 are formed in the left sideportion 101 a of the main body, which allow air to flow into the mainbody 101 from the exterior thereof.

When the heat exhausting fans 157 and 158 rotate, ambient air flows intothe main body 101 of the copying machine 100 through the intake openings165 (see FIG. 2) and passes through the air vents 168, and then the airis exhausted from the exhaust openings 166. During this process, air inthe surroundings of the image forming portion 115 and air in thesurroundings of the fixing device 122 are also exhausted together withthe ambient air.

The fixing device 122 is disposed longitudinally in a directiontransverse to the direction of sheet transportation. In other words, thefixing device 122 is disposed longitudinally in the directionperpendicular to the plane of the drawing sheets of FIGS. 2 and 3. Theheat exhausting fans 157 and 158 are arranged above and laterally offsetfrom the fixing device 122 along the longitudinal direction of thefixing device 122. By virtue of such an arrangement, it is ensured thatthe heat of the fixing device 122 can be exhausted to the exterior ofthe main body 1 of the apparatus and the fixing device 122 can becooled.

On the other hand, the ambient air also forms airflows 162 and 163passing through the air vents 162 a, 162 b, 163 a, 163 b and 164, whichare exhausted from the exhaust openings 166 and 167. Therefore, theambient air heated by the sheets S and stagnating at the deliveryportion 125 is also exhausted from the exhaust openings 166 via airvents 162 a, 162 b, 163 a, 163 b and 164. Therefore, the deliveryportion 125, the sheets S stacked on the delivery portion 125, thefixing device 122 and the sheet transport path 153 disposed downstreamof the fixing device 122 are cooled.

It should be noted that the number of heat exhausting fans is notlimited to two, but it may be one or more than two. In the case in whichthe number of the heat exhausting fan is one, it is preferable that theheat exhausting fan be disposed in such a way as to be opposed to themid-portion in the longitudinal direction of the fixing device 122.

The heat exhausting fan(s) is not necessarily required to be provided onthe jammed sheet clearance door 159, but the heat exhausting fan(s) maybe provided on the main body 101 of the apparatus.

As per the above, since the copying machine 100 according to the firstembodiment is so configured that the air in the vicinity of the fixingdevice 122, which is a source of heat, is exhausted immediately by theheat exhausting fans 157 and 158, air heated by fixing device 122 israrely transferred to other processing units such as the rotarydeveloping unit 151 and the intermediate transfer belt 152 etc.Therefore, efficient heat exhausting is made possible and it is possibleto prevent troubles such as toner blocking or fusion bond of toner fromoccurring.

Furthermore, the copying machine 100 according to the first embodimentis configured to also exhaust the air in the space between the fixingdevice 122 and the delivery portion 125, so that the sheets S arecooled. Therefore, it is possible to reduce the temperature of thesheets S in the delivery portion 125 so as to prevent delivered sheetadhesion from occurring.

(Copying Machine According to Second Embodiment)

In the following, a copying machine according to a second embodiment ofthe invention will be described with reference to FIGS. 4 and 5. FIG. 4is a plan view of the copying machine and FIG. 5 is a cross sectionalfront view of the copying machine.

The copying machine 200 according to the second embodiment differs fromthe copying machine 100 according to the first embodiment in that ajammed sheet clearance door 159 is provided on the main body 101 of theapparatus in such a way that it is openable and closable and heatexhaust fans 157 and 158 are provided on that jammed sheet clearancedoor 159. In the copying machine 200 according to the second embodiment,the same parts as those in the copying machine 100 according to thefirst embodiment are designated with the same reference signs and thedescriptions thereof will be omitted.

The heat exhausting fans 157 and 158 are provided on the inner surface159 a of the jammed sheet clearance door 159 that is provided at theright side wall of the copying machine 200. The hinge portion 161 of thejammed sheet clearance door 159 is disposed on the rear side of thecopying machine to support the jammed sheet clearance door 159 so thatthe jammed sheet clearance door 159 is pivotable with respect to themain body 101 of the apparatus.

Upon replacing the heat exhausting fans 157 and 158 for any trouble orupon performing maintenance of the heat exhausting fans 157 and 158, aservice person will open the jammed sheet clearance door 159 by swingingit with the hinge portion 161 being the pivot. Then, the service personcan perform the replacement of the heat exhausting fans 157 and 158 orother maintenance operations from the front side of the copying machine200, and therefore the time required for the replacement operation ofthe heat exhausting fans 157 and 158 or the time required for themaintenance operations can be reduced. In addition, since the heatexhausting fans 157 and 158 are supported by the jammed sheet clearancedoor 159, the maintenance operations can be performed very easily.Furthermore, since the down time of the copying machine 200 can also bereduced, it is possible to enhance the utilization efficiency of thecopying machine 200.

In addition to the above, the copying machine 200 according to thesecond embodiment has the same features as those of the copying machine100 according to the first embodiment.

In this copying machine 200 according to the second embodiment also, thenumber of heat exhausting fans is not limited to two, but it may be oneor more than two. In the case in which the number of the heat exhaustingfan is one, it is preferable that the heat exhausting fan be disposed insuch a way as to be opposed to the mid-position in the longitudinaldirection of the fixing device 122.

(Copying Machine According to Third Embodiment)

In the following, a copying machine according to a third embodiment ofthe invention will be described with reference to FIGS. 6 and 7. FIGS. 6and 7 are cross sectional views showing a portion including heatexhausting fans of the copying machine 300 according to the thirdembodiment. In the copying machine 300 according to the thirdembodiment, the same parts as those in the copying machine 100 accordingto the first embodiment are designated with the same reference signs andthe descriptions thereof will be omitted.

In the copying machine 300 according to the third embodiment, heatexhausting fans 157 and 158 are so controlled by a heat exhaust controlportion 169 that their rotating speed can be varied in accordance withtransport timing of sheets.

As the copying machine 300 performs an image forming operation, the heatexhausting fans 157 and 158 exhaust air in the surroundings of thefixing device 122 and the delivery portion 125 in the right direction ofthe main body 101 of the copying machine. On that occasion, since airflows from the air vents 164 in the wall 153 a of the sheet transportpath 153 toward the outer surface 159 b of the jammed sheet clearancedoor 159, it is possible to cause the sheet S to travel along the wall153 a of the sheet transport path 153 as shown in FIG. 6.

However, depending on the size or material of a sheet, there is a riskthat the sheet can be sucked to the wall 153 a and transport might bestopped, or the sheet can be flexed with the aid of its gravity as shownin FIG. 7 and its smooth transportation might be disturbed.

In order to prevent the above risk, when a sheet passes through thesuction area on the way from the fixing device 122 to the deliveryportion 125, the heat exhaust control portion 169 reduces the rotatingspeed of the heat exhausting fans 157 and 158 as the leading edge of thesheet approaches to the delivery roller pair 124 from the fixing device122. In addition, the heat exhaust control portion 169 is also adaptedto vary the rotating speed of the heat exhausting fans in accordancewith the properties and the size of the sheet.

Thus, in the copying machine 300, a sheet is not sucked to adhere to thewall 153 a too strongly, and therefore it is possible to transport asheet smoothly under a stable state.

In addition, in the copying machine 300, it is possible to transport asheet along the wall 153 a in the sheet transport path under a stablestate while preventing the sheet from leaning in the right or left.

In addition to the above, the copying machine 300 according to the thirdembodiment has the same features as those of the copying machine 100according to the first embodiment.

As per the above, the copying machines (i.e. image forming apparatus)100, 200 or 300 according to any of the above-described embodiments isprovided with the image forming portion (i.e. image forming means) 115for forming a toner image on a sheet, the fixing device (i.e. fixingmeans) 122 for applying heat to the sheet on which the toner image hasbeen formed by the image forming portion 115 so as to fix the tonerimage on the sheet, the delivery portion (i.e. delivering and stackingmeans) 125 on which the sheet on which the toner image has been fixed bythe fixing device 122 is delivered so as to be stacked, and the heatexhausting fans (i.e. heat exhausting means) 157 and 158 provided in thevicinity of the fixing device 122 and the delivery portion 125 forexhausting air in the surroundings of the fixing device 122 and air inthe surroundings of the delivery portion 125 from the right side portion(i.e. side portion) 101 b of the main body 101 of the apparatus. Inaddition, there is provided the air vents 162, 163 and 168 between thefixing device 122 and the heat exhausting fans 157, 158 and between thedelivery portion 125 and the heat exhausting fans 157 and 158.

With the above-described structure, since the copying machine 100, 200or 300 is so configured that the heat generated by the fixing device 122is exhausted immediately from the right side portion 101 b of the mainbody 101 of the apparatus, the heat is not transferred to otherprocessing units. Therefore, efficient heat exhausting can be realizedand it is possible to prevent troubles such as toner blocking or fusionbond of toner from occurring. In addition, it is possible to reduce thetemperature of the sheets S in the delivery portion 125 so as to preventdelivered sheet adhesion from occurring.

In the copying machine 100, 200 or 300 according to any of theabove-described embodiments, the delivery portion 125 is disposed abovethe fixing device 122, and the sheet transport path 153 arranged in thevertical direction is provided between the fixing device 122 and thedelivery portion 125, which sheet transport path 153 has air vents 164.

By virtue of this structure, the copying machine 100, 200 or 300according to any of the above-described embodiments can transport asheet under a stable state while causing the sheet to travel along thetransport path 153 without fail. In addition, since a sheet is cooled asit travels from the fixing device 122 to the delivery portion 125 andthen stacked on the delivery portion 125, it is possible to preventdelivered sheet adhesion from occurring.

The copying machine 100, 200 or 300 according to any of theabove-described embodiments is provided with the heat exhaust controlportion (i.e. heat exhaust control means) 169 that controls, while asheet is transported in the sheet transport path 153, the heatexhausting fans 157 and 158 in such a way as to reduce the amount of airexhausted by the heat exhausting fans 157 and 158 as the sheetapproaches from the fixing device 122 to the delivery portion 125.

With the above-described feature, the copying machine 100, 200 or 300according to any of the above-described embodiments can vary therotating speed of the heat exhausting fans 157 and 158 as the sheettravels through the suction area by the heat exhaust fans 157 and 158extending from the fixing device 122 and the delivery portion 125.Therefore, excessive suction of the sheet can be prevented, and it ispossible to transport the sheet stably.

In the copying machine 100, 200 or 300 according to any of theabove-described embodiments, the heat exhausting fans 157 and 158 aredisposed on the jammed sheet clearance door (or lid) 159 provided on theright side portion (i.e. side portion) 101 b of the main body 101 of theapparatus.

By virtue of this structure, the copying machine 100, 200 or 300according to any of the above-described embodiments allows easymaintenance of the heat exhaust fans 157 and 158 by detaching the jammedsheet clearance door 159 easily from the right side portion of the mainbody 101 of the apparatus.

In the copying machine 200 according to one of the embodiments, thejammed sheet clearance door 159 is provided on the right side portion(i.e, side portion) 101 b of the main body 101 of the apparatus, and itis openable and closable with its rear side end being the pivot.

With this structure, in the copying machine 200 according to one of theabove-described embodiments, a service person can have an access to theheat exhausting fans 157 and 158 from the front side of the main body101 by opening the jammed sheet clearance door 159. Therefore, it ispossible to reduce time required for service operations and also reducedown time of the image forming apparatus.

In the image forming apparatus according to the present invention, sinceheat generated by fixing means is exhausted from a side portion of themain body of the apparatus immediately, the heat is not transferred toother processing units. Therefore, it is possible to exhaust heatefficiently to prevent troubles such as toner blocking or fusion bond oftoner etc.

In addition, since air in the space between fixing means and deliveringand stacking means is exhausted, it is possible to cool sheets to reducethe temperature of the sheets in the delivering and stacking means.Therefore, delivered sheet adhesion can be prevented from occurring.

While the invention has been described with reference to the structuredisclosed herein, the invention is not confined to the details set forthand it is intended to cover such modifications or changes as may comewithin the purpose of the improvements or the scope of the followingclaims.

1. An image forming apparatus comprising: image forming means forforming a toner image on a sheet; fixing means for applying heat to thesheet on which the toner image has been formed by said image formingmeans so as to fix the toner image to the sheet; delivering and stackingmeans on which the sheet, on which the toner image has been fixed bysaid fixing means, is to be delivered and stacked; and heat exhaustingmeans provided in a vicinity of said fixing means and said deliveringand stacking means, for exhausting air from surroundings of said fixingmeans and air from surroundings of said delivering and stacking meansfrom a side portion of a main body of the apparatus, wherein air ventsare provided between said fixing means and said heat exhausting meansand between said delivering and stacking means and said heat exhaustingmeans, respectively, and wherein said delivering and stacking means isdisposed above said fixing means, and said image forming apparatusfurther comprises a sheet transport path arranged in a verticaldirection between said fixing means and said delivering and stackingmeans, said sheet transport path having an air vent.
 2. An image formingapparatus according to claim 1, further comprising heat exhaust controlmeans for controlling, while the sheet is transported in said sheettransport path, said heat exhausting means in such a way as to reduce anair exhaust amount of said heat exhausting means as the sheet approachesfrom said fixing means to said delivering and stacking means.
 3. Animage forming apparatus according to any one of claim 1 or 2, whereinsaid heat exhausting means is disposed on a lid that is provided on aside portion of the main body of the apparatus.
 4. An image formingapparatus according to claim 3, wherein said lid is provided in such away that said lid is openable and closable with a pivot being located ona rear side of said side portion of the main body of the apparatus. 5.An image forming apparatus comprising: a fixing roller for fixing atoner image formed on a sheet to the sheet; a delivery roller fordelivering the sheet on which the image has been fixed by said fixingroller; a stacking tray on which the sheet delivered by said deliveryroller is to be stacked; a guide for guiding the sheet from said fixingroller to said delivery roller; a housing in which said fixing rollerand said guide is contained; a delivery tray side air vent provided insaid housing for taking in air from a space above said stacking tray toa vicinity of said guide; and a fan provided on a side opposite to saiddelivery tray side air vent with said guide interposed therebetween toexhaust air in a vicinity of said fixing roller and air in the vicinityof said guide to an outside of said housing.
 6. An image formingapparatus according to claim 5, wherein said guide guides the sheetupwardly.
 7. An image forming apparatus according to claim 6, whereinimage reading means is provided above said stacking tray and saidstacking tray side air vent.
 8. An image forming apparatus according toany of claims 5 to 7, wherein an air vent for allowing airflow from saiddelivery tray side air vent to said fan is provided in said guide.
 9. Animage forming apparatus with heat exhausting means, comprising: imageforming means for forming a toner image on a sheet; fixing means forapplying heat to the sheet on which the toner image has been formed bysaid image forming means so as to fix the toner image to the sheet;delivering and stacking means on which the sheet, on which the tonerimage has been fixed by said fixing means, is to be delivered andstacked; and heat exhausting means provided in a vicinity of said fixingmeans and said delivering and stacking means, for exhausting air fromsurroundings of said fixing means and air from surroundings of saiddelivering and stacking means from a side portion of a main body of theapparatus, wherein air vents are provided between said fixing means andsaid heat exhausting means and between said delivering and stackingmeans and said heat exhausting means, respectively, and wherein saidheat exhausting means is disposed on a lid that is provided on a sideportion of the main body of the apparatus.
 10. An image formingapparatus according to claim 9, wherein said lid is provided in such away that said lid is openable and closable with a pivot being located ona rear side of said side portion of the main body of the apparatus.